This book describes the application of new high temperature superconducting materials to microwave devices and systems. It deals with the fundamentals of the interaction between microwaves and superconductors, and includes a basic description of how microwave devices can be constructed using these materials. Since the discovery of high temperature superconductors in 1986 there has been an enormous effort worldwide to develop and characterize these materials. Work on applications has proceeded more slowly however. Nevertheless, commercial applications are now beginning to arise, including use...